Automatic telephone switch for hearing aid

Abstract

A hearing aid is provided with a switch that automatically switches the hearing aid input from a microphone input to a voice coil input in the presence of a magnetic field. The magnetic field can be generated by a magnet in a telephone handset.

What is claimed is:  
     
       1. A hearing aid comprising: 
       a microphone adapted to output a first signal based on an acoustic input:  
       a voice coil pickup adapted to output a second signal based on an electromagnetic input;  
       a signal processing circuit for processing the first signal and the second signal; and  
       a switching circuit coupled to the microphone and to the voice coil pickup, wherein the switching circuit includes a magnetically actuated switch which energizes a voice coil circuit that includes the voice coil pickup and the signal processing circuit, and de-energizes a microphone circuit that includes the microphone and the signal processing circuit, wherein the switching circuit includes:  
       a first transistor having a collector coupled to the microphone, a base connected to a first node, and an emitter coupled to ground;  
       a second transistor having a collector coupled to a second node, a base connected to the first node, and an emitter coupled to ground;  
       a third transistor having a collector connected to the voice coil pickup, a base connected to the second node, and an emitter coupled to ground; and  
       the magnetically actuated switch having a first contact connected to the first node and a second contact connected to ground.  
     
     
       2. The hearing aid of  claim 1 , wherein in a first state the first and second contacts are open, in a second state the first and second contacts are closed shorting the base of the first transistor and the base of the second transistor to ground, operatively coupling the voice coil pickup to the signal processing circuit. 
     
     
       3. The hearing aid of  claim 1 , wherein the first node is coupled to a hearing aid voltage source through a resistor, and the second node is coupled to the hearing aid voltage source through a resistor. 
     
     
       4. The hearing aid of  claim 1 , wherein the signal processing circuit is adapted to provide noise reduction and tone control. 
     
     
       5. The hearing aid of  claim 1 , wherein the magnetically actuated switch is a reed switch. 
     
     
       6. A hearing aid comprising: 
       a switching circuit;  
       a signal processing circuit coupled to the switching circuit;  
       a microphone coupled between the switching circuit and the signal processing circuit; and  
       a voice coil pickup coupled between the switching circuit and the signal processing circuit, wherein the switching circuit includes:  
       a microphone switch coupled between the microphone and ground;  
       a second switch coupled between a voltage source node and ground;  
       a voice coil activating switch coupled between the voice coil pickup and ground; and  
       a magnetically activated switch coupled between the voltage source node and ground, wherein the voltage source node is adapted to contact a hearing aid voltage source.  
     
     
       7. The hearing aid of  claim 6 , wherein the second switch is further coupled between the magnetically activated switch and the voice coil activating switch. 
     
     
       8. The hearing aid of  claim 6 , wherein each of the second switch, the microphone switch, and the voice coil activating switch includes a transistor. 
     
     
       9. The hearing aid of  claim 6 , wherein the hearing aid is an in-the-ear hearing aid. 
     
     
       10. The hearing aid of  claim 6 , wherein the signal processing circuit is adapted to provide noise reduction and tone control. 
     
     
       11. The hearing aid of  claim 6 , wherein the magnetically actuated switch is a reed switch. 
     
     
       12. A hearing aid system comprising a telephone handset and a hearing aid, the telephone handset having a magnet, and the hearing aid comprising: 
       a microphone adapted to output a first signal based on acoustic input,  
       a voice coil pickup adapted to output a second signal based on electromagnetic input,  
       a switching circuit having two transistor switches, the switching circuit connected to the microphone and the voice coil pickup, the switching circuit automatically transmitting the first signal with one transistor switch conducting in the absence of the magnetic field produced by the magnet and automatically transmitting the second signal with the other transistor switch conducting in the presence of the magnet;  
       a signal processing circuit connected to the switching circuit, the signal processing circuit receiving the signal transmitted by the switching circuit, wherein the hearing aid includes a voltage source and the switching circuit includes:  
       a first transistor having a collector connected to the microphone, a base connected to a first node of the voltage source, and an emitter connected to the signal processing circuit;  
       a second transistor having a collector connected to a second node of the voltage source, a base connected to the first node, and an emitter connected to ground;  
       a third transistor having a collector connected to the voice coil pickup, a base connected to the second node, and an emitter connected to the signal processing circuit; and  
       a magnetically actuated switch having a first contact connected to the first node and a second contact connected to ground, in a default state the first and second contacts are open, in an activated state the first and second contacts are closed, the base of the first transistor and the base of the second transistor are shorted to ground and the third transistor connects the voice coil pickup to the signal processing circuit.  
     
     
       13. The hearing aid of  claim 12 , wherein the signal processing circuit is adapted to provide noise reduction and tone control. 
     
     
       14. The hearing aid of  claim 12 , wherein the magnetically actuated switch is a reed switch.